Chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) compounds have been used as refrigerants, fire extinguishing agents, propellants, and solvents since the early twentieth century. However, CFC and HCFC are now believed to deplete the ozone layer of the earth via UV-promoted reactions. As a result, the U.S. Environmental Protection Agency has already banned the production and importation of certain CFC and HCFC products.
Internationally, the Montreal Protocol has set out plans for replacing CFC and HCFC compounds with hydrofluorocarbon (HFC) compounds. However, the cost of producing HFC compounds is considerably higher than that of producing CFC or HCFC compounds. Presently, industrial fluorination processes for producing HFC are based on hydrogen fluoride (HF) fluorination of chlorocarbons. FIG. 1 presents examples of known potential multistep routes to produce CFC-113.
As illustrated in FIG. 1, HFC-125 can be produced with either 1,1,2-trichloroethene (triclene) or 1,1,2,2-tetrachloroethene (perclene) using multistep processes. For example, HFC-125 can be produced by first converting either triclene or perclene into 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123) and then fluorinating HCFC-123 to 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124). HFC-125 can then be produced by performing chlorine-fluorine exchange on HCFC-124 with hydrogen fluoride.
The processes for producing HFC-125 are more complex, both chemically and operationally, than those for CFC and HCFC compounds. Moreover, both the triclene and perclene processes require disposing of hydrogen chloride (HCl) byproducts. Procedures and equipment are available to convert some of the HCl byproducts into a chlorine (Cl2) gas and subsequently recycle the chlorine gas back into the production process. Nonetheless, this recycling operation adds to the cost of the overall HFC production process.